The annual 26.2-mile run is scheduled for Oct. 9, the day after The Jewish Day of Atonement, the holiest day on the Jewish calendar. Yom Kippur "requires worshippers to fast, abstaining from food and drink for a 25-hour period, and observant runners will only be able to break the fast the night before the marathon," Lee wrote.

Experts gave conflicting views on whether it's safe to run a marathon after prolonged fasting. According to Lee's piece, Dr. Sara Brown, a sports physician in Lincoln Park, said fasting runners should sit out the marathon, adding that long runs after fasting can be dangerous.

"That's what I would recommend to anybody that would be observing the holiday," Brown said. "I wouldn't recommend running 26 miles the next day."

However, Chicago marathon Race Director Dr. George Chiampas said some runners who fast can run the next day and that a 24-hour fast would not harm the body enough to be dangerous if a runner has the proper nutrients.

"If they've done it in the past, and they feel they can get back to baseline, that should suffice," Chiampas said. "It's not a generalization for every runner."